1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer and a copying machine, and a printing control method therefore.
2. Description of Related Art
Image forming apparatus having a two-sided printing mechanism for automatically printing images on both of the front and back sides of a supplied paper sheet and discharging the image printed paper sheet to a discharge position is conventionally known. In the case that printing is executed in a two-sided printing mode in such a kind of image forming apparatus (so-called a two-sided printing apparatus), a paper sheet set in a paper feed position such as a paper feed cassette, a manual paper feed tray or the like is fed to an image forming section, and an image is printed on one surface (the first surface or the front side) of the paper sheet. Thereafter the paper sheet is reversed in the apparatus and fed to the image forming section again and an image is printed on the remaining one surface (the second surface or the back side) of the paper sheet. The paper sheet with images printed on both of the front and back sides (the first and second surfaces) thereof in such a manner is discharged to a discharge position such as a discharge tray outside the apparatus and thereby the two-sided printing can be achieved by a single paper feed from the paper feed position (see, for example, Japanese Unexamined Patent Publication No. 7-271508).
However, in order to realize such a two-sided printing mechanism as abovementioned, a device (so-called a switch-back device) for reversing the front side (the first surface) printed paper sheet in the image forming apparatus is required, and thereby the whole structure of the image forming apparatus grows in size and the manufacturing cost thereof becomes high.
Therefore, it is thought that the two-sided printing is executed using an image forming apparatus having no two-sided printing mechanism (so-called a one-sided printing machine). In other words, printing images on two sides of a paper sheet can be achieved by the steps of feeding a paper sheet set in the paper feed position to the image forming section, printing an image on one side (the first surface or front side) of the paper sheet, thereafter discharging the printed paper sheet to the discharge position outside the apparatus, feeding the paper sheet to the image forming position in response to a user's setting again the paper sheet in the paper feed position, and printing an image on the other side (the second surface or back side) of the paper sheet (see, for example, Japanese Unexamined Patent Publication Nos. 2004-279499 and 2004-279451).
In two-sided printing methods using a so-called one-sided printer such as those disclosed in Japanese Unexamined Patent Publication Nos. 2004-279449 and 2004-279451, “a manual paper feed two-sided printing mode” is provided for facilitating the two-sided printing in some cases. Taking of such a printer provided with “a manual paper feed two-sided printing mode” as an example, in the manual paper feed two-sided printing mode, a message meaning “Set the printed paper sheet on the manual paper feed tray and then press the OK button” is pop-up displayed in a user's personal computer connected to the printer after an image is printed on one side of a paper sheet. That is, processes and operations to be executed by the user are informed to the user.
However, such a conventional apparatus has a disadvantage that, if other paper sheet than the printed paper sheet has been set on the manual paper feed tray when the user erroneously presses the OK button, the conventional printer starts feeding the paper from the manual paper feed tray and executes the back side printing no matter whether it is the front side printed paper sheet or not.
Further, such a conventional apparatus has another disadvantage that, after the front side printing ends, according to the informed processes/operations, the user has to go to the printer and set the front side printed paper sheet on the manual paper feed tray, then return to his (her) seat again and click the OK button of the personal computer. Thus, the user is compelled to execute inefficient operations.
Further, such a conventional apparatus has a further disadvantage that, in the manual paper feed two-sided printing mode, if the user fails to set the front side printed paper sheet on the manual paper feed tray after the front side printing, the printer remains in the manual paper feed two-sided printing mode and cannot accept or execute any printing demand (another job) transmitted from another personal computer and the like.
Furthermore, such a conventional apparatus has a disadvantage that, if it is so arranged that another job is acceptable in the two-sided printing mode, sometimes the two-sided printing cannot be correctly executed and erroneous printing is done.